Such a combination is known in practice and described, for instance, in U.S. Pat. No. 4,861,520, which is herewith incorporated by reference.
For local radioactive radiation treatment of a specific internal area of the human body, such as a tumor, or a wall section of a blood vessel, it is possible, as described in U.S. Pat. No. 4,861,520, to deliver a capsule with a radioactive source, via a hollow needle, a flexible tube or a catheter or the like, to the area to be treated. For this purpose, normally the so-called "after loading" technique is employed. First, the catheter, or the like, is placed in the body and then the capsule attached to the distal end of a guidewire is delivered with the help of a remotely controlled device to the treatment area.
The combination of the capsule and guidewire should, on the one hand, have a high degree of flexibility to be able to follow the curves of a catheter or the like, and on the other, a certain rigidity, so that the capsule can be pushed through a catheter toward its distal end with the help of the guidewire. For the application in endovascular brachytherapy, a catheter normally has an inside diameter on the order of 1.5 mm or less. The length of a capsule depends on the desired strength of the radioactive source placed in the capsule, but should be on the order of several times the diameter, for instance in the range of 5 to 7 mm. The capsule itself and its connection with the guidewire are not flexible, so that the front part of the combination of guidewire and capsule has a relatively low degree of flexibility. Thus there is a certain probability that the capsule cannot pass the curves in a catheter with a strong curvature or only passes with difficulty.